Not calculating anything at the moment. The black figure/image and purple CAD data are both set for straight line length=55. The red vertical dimensions are Surfding’s rockers and the purple ones are for the Lis-like CAD data I have been toying with.
So, trigonometry aside, your comments would indicate flatter is mo’ bettah for a smaller fish, yes?
Yes, I would not go greater than Surfding’s rocker ratios/shapes for a 4-7.
Max values for 4-7:
Nose rocker at tip = (55/66) 0.833 X 3.4” = 2.83”
Tail rocker at tip/end = 0.833 X 1.5” = 1.25”
Zero rocker curve point for the 4-7 would be at 30.94” from tail.
I had to know.
I plotted the Kinstle Lis Fish Rocker values from 37” to 65”.
Removed outlier value at 65”.
Generated an equation.
Added a new 65” value generated with first equation. Cleaned up the data set using first equation generated.
Created a new equation and new rocker data.
Assuming a straight-line rocker from 0"-37” from the tail, these data will give you a nice clean curve from 37"-65” from the tail (R^2 = 1.0).
@stoneburner Your deck rocker is very nice.
I started the bottom based on your numbers+book values
See what you think
I used the rocker numbers from the Kinstle book table.
My assumption is that the book table numbers are for bottom rocker.
If you lay the rear section (0-37) flat, max nose bottom rocker would then be 3.19” which might work for a Lis Fish kneeboard — fairly gentle entry rocker angle with flat tail rocker (more like a body/belly/Paipo board).
My equation numbers were just to see what the computer regression would do with the Kinstle bottom (table) rocker numbers.
Not sure I see how you arrived at your “bottom rocker” numbers.
The nose bottom curve “seems” a bit steep for a Lis Fish Kneeboard. But if it is 3.08” up from the zero curve (tangential) point of a rocker bar, it might work for a 65” Retro (Lis) Fish.
Then there is the possibility that the book numbers for a 65” Retro Fish were not well suited for modern SB style performance. Only one way to find out…
I found this old photo of the fish I made. I don’t know the rocker numbers, but the XPS foam was 3" thick. I know it has some tail rocker, I think it might be between 1.5" and 2" of tail rocker. It was 5’ 3" long.
Mahalo Harry, I appreciate the input.
Bill, I went back and looked at Kinstle’s notes/methods on rocker measurement. He is biased towards designs that are flat on the bottom, though he does mention ‘some’ surfboards may have tail rocker and need to be measured in a different way…
So, taking your cleaned-up curve as bottom rocker instead of deck rocker (I like it better as deck rocker 
)…
Did the TSJ article suggest a rocker, or a blank, or to use a broken board as a start, and/or to make the bottom flat?
Jim,
I never saw the TSJ article, only found the PDF template.
My equation work here was done out of curiosity to see what I could get the computer to do with the Kinstle rocker data.
My policy on curves is, if I like a curve for any design feature, I use it. 
At this point, I suspect you know I like to combine (mix and match) fluid dynamics and geometric curves/equations to design surfboards. I found trigonometry can be useful too (really just right triangle math).
My designs/methods have come a long way from the quarter-inch blue line graph paper approach I learned in high school wood shop.
My computer makes some nice clean curves and gives me equations that replicate them accurately and precisely.
I had the board under my house, so measured it today.
1.5" tail rocker and almost 3" nose rocker.
Mike (Rooster) sent me his 72” Lis Fish template 7.5 years ago.
He said the rocker he used for it was 3.5” nose and 1.5” tail — consistent with a gentle/shallow rocker curve.
That scales down to 3.16” nose and 1.35” tail for a 65” Lis Fish.
Thanks Harry, thanks Bill.
Here is how the TSJ 4-7 outline compares to the Kinstle numbers for a Lis 5-5:
No issue with the book dims yielding a reasonable set of curves for the plan shape. But we are seeing an example where tail width and wide points dims are similar between the two, but board length and nose shape are not.
Nice overlay comparison Jim.
Looks like Steve Lis just extended the curve lines of his personal 4-7 kneeboard to create the 5-5 standup model for Jeff Ching.
Provides some interesting design evolution insight.
Would have been easy to do with a batten.
